Why one good result tells you nothing
A converter that nails a clean vocal can turn a four-note chord into mush and skip half the notes in a fast bassline. Forum threads keep asking which tool is "best" anyway. One posted on Audiosex on November 12, 2026 asks exactly that: Best MIDI Transcribe (Audio to Midi) plugin/software?. The thread shows the question and a list of other threads, but no method for judging any answer.
The method below fills that gap. It works on any converter, free or paid, including the audio-to-MIDI command in your DAW if it has one. You run it on your own recordings, so the result reflects your material, not someone else's demo.
Step 1: Build a fair project
Set tempo and sample rate
Create a new project at the tempo of your source recordings. If you don't know it, find it first and type it in, then turn off any warping or tempo-follow features. Set the project to 44.1 kHz or 48 kHz, whichever matches your source files, so nothing gets resampled before the converter sees it.
Watch for converters that write their own tempo changes into the MIDI file. If one does, the notes will appear to drift even when the detection is fine. Delete the embedded tempo map or import notes only.
Pick three test clips
Use short clips, roughly 8 bars or 15 to 30 seconds each, so you can score them quickly. Each clip exposes a different weakness.
The first is a monophonic bass or vocal line. This is the easiest case and sets your baseline. If a tool fails here, stop testing it.
The second is a polyphonic chord part, such as piano, guitar or keys with three or four notes sounding at once. Chords are where many converters lose notes or collapse voices into one. A tool's documentation should say whether it handles polyphony at all, and this clip lets you confirm it.
The third is a loop with fast notes, such as sixteenth-note bass or an arpeggio. Fast, repeated pitches punish weak onset detection and show how a converter treats short notes.
Write an answer key
Before converting anything, spend five minutes writing the expected notes into a piano roll on a muted track. Use parts you played yourself or already know, so you aren't guessing what is correct. The answer key turns "it sounds off" into countable errors. See read about varispeed vs time stretch for sampling: a daw exercise for additional background.
It's optional if you can hear mistakes reliably, but scoring gets slower and less consistent without it.
Create one shared instrument track
Load one simple patch, such as a plain piano or a clean sine or saw bass. Route every converted MIDI part to a copy of that exact patch with identical settings. Skip patches with heavy release, reverb or random modulation, because they blur the differences you're trying to hear. Keep the original audio on its own track so you can mute and solo it against each result.
Step 2: Convert and level-match
Run each clip through each converter using default settings first. Tweak sensitivity or pitch-range options later, and note whenever you change one. Drag every result onto its own MIDI track with the shared patch.
Then bounce each MIDI track's audio and level-match the bounces to within about 0.5 dB. Use integrated LUFS if your meter offers it, or RMS if not. Louder playback reads as more accurate, and different converters assign different velocities, which changes loudness on the same patch.
Match with a gain trim on the bounce. Don't edit velocities to fix loudness, because you score velocity accuracy separately.
Step 3: Run the 30-minute session
This order fits two or three converters in about half an hour. Add roughly ten minutes for each extra converter.
- Spend about 8 minutes building the project, importing the clips and creating the shared patch tracks.
- Spend about 7 minutes converting all three clips with each tool and importing the MIDI.
- Spend about 5 minutes bouncing and level-matching to the 0.5 dB target.
- Spend about 10 minutes scoring each result against the original and the answer key, using the sheet below.
Listen to the original, then one result, then the original again. If you can, switch between converters on the same clip without looking at the names. Then open the piano roll and check what your ears told you.
Step 4: Score what you hear and see
Count errors per clip rather than going on overall impression. Print the sheet below or copy it into a note.
| Check | What to look for | How to score | |---|---|---| | Missed notes | Notes in the answer key with no MIDI note | Count them | | Ghost notes | Extra notes where the source has none, often on decay, noise or breaths | Count them | | Octave errors | Correct note name, wrong octave, common on bass and low vocals | Count them | | Timing offset | Note starts early or late against the audio transient. Compare bar 1 with the last bar to spot drift | 0 = tight, 1 = slightly loose, 2 = obviously off, 3 = drifting | | Note length | Notes cut short, run together or hanging past the release | 0 to 3 | | Velocity | Does the dynamic shape follow the original performance, or is everything one value? | 0 to 3 | | Cleanup time | Minutes with a stopwatch to make the part usable | Cap at 5 minutes per clip |
Some of these errors cost more to fix than others. Octave errors are cheap if they're consistent, since you can transpose a region, and expensive if they're scattered. Ghost notes are usually faster to delete than missed notes are to add. Timing drift that grows across the clip is a worse sign than a constant offset, which you can slide.
Quantizing can hide timing problems, so score timing before you quantize anything.
Step 5: Time the cleanup and compare it to replaying the part
Cleanup time decides most real-world choices. For each result, start a stopwatch and fix the part until it plays correctly on the shared patch, then stop. If you hit the 5-minute cap, mark it as a fail.
Next, time how long it takes to play or program the same part from scratch. As a rule of thumb (this is an inference, not a measured figure), if cleanup regularly takes longer than replaying, the converter isn't helping on that kind of part. That often happens with dense chords, where fixing a missed voicing means entering the notes by hand anyway. Replaying also wins when the original performance was sloppy, since you'd be cleaning up your own mistakes twice.
Also read: full coverage of roli seaboard after administration: keep, sell or switch
Step 6: Turn scores into a pick
Compare totals per clip, not just overall. A tool that wins on two clips and fails the third may still be the right choice if you never record that third type of material.
If you mostly convert single-line vocals and basslines, choose the tool with the fewest octave errors and the best timing on clips one and three. Ignore its chord score.
If you work with guitar, piano or pads, weight the chord clip most heavily. A converter that drops notes there will cost you more than any gain on monophonic parts. Ask whether any result got close enough that cleanup beat replaying.
If you handle fast parts, look at missed notes and note length on the loop first. Poor onset detection shows up there before anywhere else.
For free versus paid, compare cleanup minutes, not feature lists. If a free tool lands within a minute or so of a paid one on your clips, take the free one. If the paid tool saves several minutes per part and you convert parts often, that time pays for it. The Audiosex thread gives no prices or version details, so check current pricing and trial terms on each vendor's own page before buying.
If every tool fails on your hardest clip, that's a result too. Plan to replay those parts and use conversion only where it demonstrably saves time.
What to expect next
Once you have scores for one set of clips, rerun the test whenever a converter updates or you start recording a different instrument. Keep your answer keys and project template so a repeat takes far less than 30 minutes. If you later get listening files from a vendor or a producer you trust, drop them in as a fourth clip and score them the same way.
